Electrode Reaction at Platinum/Ceria Surface Modified YSZ Interface

The electrode reaction was examined on ceria coated YSZ by a platinum point electrode in H-2-H2O atmosphere at 973 K-1173 K. The thickness of the ceria coating layer was altered from 0 to 2.5 mu m, fabricated by a laser ablation and by a vacuum vapor deposition method on YSZ single crystals. The electrode / electrolyte interface conductivity increased with 1/4 powers of p(H-2) and p(H2O) on both ceria coated and non-coated YSZ. The interface conductivity was significantly improved on a thicker ceria coating surface than 1 mu m. The effective electrode reaction radius also increased in a thick ceria coating. The O-18/O-16 exchange experiment at low oxygen partial pressure revealed that the oxygen surface exchange rate of ceria is not high compared with that of YSZ. It can be concluded that the bulk ionic conduction of ceria makes a more effective contribution to the electrode reaction than the surface catalytic activity in H-2-H2O atmosphere.